Discount validy period not specified

I am quite dissatisfied.Since Ismail & Dahya Attorney gave me a 30% discount on August 28th, When I asked for the settlement letter with the discount to settle the account on the 3rd, I was informed that I was not eligible for the reduction. After receiving the SMS to verify that, how so? They now want that I pay the entire outstanding balance. Why give a discount that doesn't specify its duration of validity? Even though I rep**** inside the allotted time, their consultant claimed that the discount period was over when I tried to clarify that the seven days had not yet expired. Why No spicify the discount validy period on your communication. I want to settle the account can someone assist me please .your consultant dont want to listen all they say is I dont qualify for discount even when i proof it was provided by you guys